As is known, the car rear lights usually consist of a rigid rear body which is substantially basin-like in shape and is structured so as be firmly fitted into a specially provided seat made in the rear of the vehicle's body; a front lenticular semi-shell which is at least partially made of a transparent or semi-transparent plastic material, usually coloured, and which is placed to close the mouth of the body so as to surface from the vehicle's body; one or more cup-shaped reflectors with a more or less parabolic profile, each of which is located inside the rear body with its mouth facing a corresponding transparent or semi-transparent portion of the front lenticular semi-shell; and one or more incandescent lamps, each of which is arranged close to the bottom of a respective cup-shaped reflector so as to backlight a portion of the front lenticular semi-shell directly above the same cup-shaped reflector.
In some models of car rear lights, the front lenticular semi-shell is also provided with one or more supplementary transparent or semi-transparent portions having a narrow and elongated shape, i.e. a band-like shape, which usually flanks the main transparent or semi-transparent portion(s) of the front lenticular semi-shell, i.e. the transparent or semi-transparent portions aligned with the mouths of the cup-shaped reflectors.
The backlighting of each supplementary band-like, transparent or semi-transparent portion of the front lenticular semi-shell is usually achieved by means of a light-guiding plate made of a photoconductive material, which more or less has a thickness equal to the width of the supplementary band-like portion, extends from the bottom of the casing almost up to the back of the front lenticular semi-shell, locally remaining substantially perpendicular to the lenticular semi-shell, and is then shaped such that its front lateral side is located just behind the supplementary band-like portion of the semi-shell for the entire length of the same portion; and a row of light emitting diodes, traditionally called LEDs, which are located on the bottom of the body, resting on the rear lateral side of the light-guiding plate, and are orientated so as direct the light produced towards the inside of the plate through the latter's rear lateral side. Light that then travels inside the body of the light-guiding plate according to the same physical principles that govern light propagation in fibre-optic cables and finally comes out of the light-guiding plate through the front lateral side of the same plate.
Although guaranteeing a significant cost saving with respect to a backlighting system that uses an array of LEDs located immediately beneath the supplementary band-like, transparent or semi-transparent portion of the lenticular semi-shell, the backlighting system with a light-guiding plate does not allow making supplementary band-like, transparent or semi-transparent portions wider than 10-15 millimetres because the thickness of the light-guiding plate would reach values incompatible with the constructional specifications for the rear lights of cars.